1. Field of the Invention
This invention relates to an improvement of an apparatus for observing or photographing an endothelium of a cornea of an eye to be tested by irradiating illumination light toward the cornea.
2. Prior Art
Heretofore, there is known a contact type apparatus as an apparatus For observing or photographing an image of an endothelium of the cornea of the eye. For observing or photographing the endothelium of tile cornea of a person to be tested (patient) using this apparatus, narcotic eye lotion is applied to the eye and then a cone lens is contacted on the surface of the cornea. However, in this contact type apparatus, there is a possibility that the surface of the cornea is damaged by the cone lens. In addition, it has such a shortcoming that much time and labor are required to disinfect the cone lens, and the like.
In view of tile above, a non-contact type apparatus has been developed, in which an optical attachment for observing the endothelium of tile cornea is attached to a slit lamp, and an image of the endothelium is observed or photographed with the aid of this optical attachment.
The non-contact type apparatus is used as follows. The operator (person who examines the eye) roughly adjusts or aligns, by eye measurement, the relative positional relationship between the eye to be tested and tile apparatus optical system. Thereafter, the patient is requested to gaze at a fixation mark and the cornea of the patient is illuminated in that condition. Then, the operator observes or photographs the endothelium of the cornea under the light flux of reflected light from the cornea which is irradiated. In the conventional non-contact type apparatus thus constructed, a fixation lamp serving as the fixation mark is located outside the apparatus body.
This fixation lamp can be moved freely. However, since there is no correlation between the fixation lamp and the apparatus optical system, it is very difficult to make the alignment and the possibility for successfully photographing the endothelium of the cornea is low. This often renders a large burden onto not only the examiner but also the patient.
In the operation for treating, For example, cataract or the like, that an upper part of the cornea is usually cut out in order to insert an intraocular lens therein. Therefore, that part of the cornea which is cut out is damaged. In order to judge recovery of the cornea after an operation, it is necessary to determine how far the cornea has been damaged after the operation compared with the state of the corneas before the operation. However, in the conventional apparatus, this need cannot be satisfied because there is no way to determine which part of the cornea is observed or photographed.
Furthermore, the conventional non-contact type apparatus does not include an optical system adapted to observe the anterior portion with low magnification. As a result, when the endothelium of that part of the cornea other than the central portion of the cornea is observed from the front, it is difficult to determine which part of the cornea is represented by the image of the endothelium under observation because the optical system for observing the endothelium has high magnification.